Mobile machines have been used at worksites such as mines, construction zones, and/or other similar environments to lift, carry, relocate, excavate, and/or otherwise act on material at the worksite. For example, a number of loaders may be used at a mine or other like excavation site to remove earthen material and transport the material to a waiting haul truck. Typically, such loaders are wheeled or tracked vehicles having a large work tool, such as a bucket, at one end thereof. Such loaders also typically include various linkages and actuators used for raising, lowering, racking, unracking, and/or otherwise manipulating the work tool.
In various applications, it may be useful to know the weight of a payload carried by the work tool of such vehicles. For example, on-highway haul trucks must abide by laws restricting the total weight of the material carried in their beds. Depending on the density and other characteristics of the payload deposited into haul truck beds by the loaders described above, it may be possible to load more than the maximum allowed weight into the bed of such trucks. In addition to violating applicable laws, such excessive weights may also have a detrimental effect on the suspension, drive train, and/or other components of the haul truck. Moreover, in mining and/or other applications in which material is sold according to weight, knowing the weight of the payload carried by such loaders, and deposited into the respective haul truck beds, may be paramount to calculating an accurate cost of the loaded material.
Typically, loaders used in such applications include payload systems configured to determine the weight of the payload carried by their respective work tools in real time. Occasionally, such systems must be calibrated at the worksite to ensure consistent and accurate weight determinations. Calibrating these systems generally requires either a large scale onto which the loader may be driven while carrying a payload, or a large object having a precisely-known weight sufficient for loading the actuators and/or linkages associated with the work tool. Often, however, neither a large enough scale nor a large object of known weight is present at the worksite. In order to calibrate the payload system in such situations, it may be necessary to determine the weight of a payload carried by work tool using other means.
U.S. Pat. No. 5,929,389 to Keuper, issued Jul. 27, 1999 (“the '389 patent”), describes an exemplary system for determining the weight of a load carried by a mobile vehicle. The system disclosed in the '389 patent includes a hydraulic cylinder used to raise and lower the load, a pressure sensor for measuring the pressure of the hydraulic cylinder, and a position sensor for measuring the position of a linkage associated with the cylinder. The system of the '389 patent also includes a pitch sensor for measuring the pitch of the vehicle and a processor in communication with the pressure, position, and pitch sensors. According to the '389 patent, the processor may be able to determine the weight of the load carried by the vehicle based on signals received from the respective sensors.
Although the system of the '389 patent may be capable of determining the weight of a load carried by a vehicle, such systems may not be relied upon to provide an accurate measurement of weight. For example, the disclosed system measures only a single pressure associated with a single hydraulic cylinder of the vehicle. Additionally, the disclosed system and/or weight determination method does not include provisions minimizing the effects of system friction, cylinder seal resistance, and/or other sources of measurement error. Moreover, the disclosed method does not locate the linkages of the vehicle at a repeatable reference position when measuring the various pressures, positions, etc. Due to these factors, the resulting weight determination made by the system of the '389 patent may not be sufficiently accurate for calibration purposes.
The disclosed embodiments are directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.